Although EEG sleep changes are an important psychobiologic marker in adult affective disorders, sleep studies of children and adolescents with major depressive disorder (MDD) have revealed conflicting results. In studies of adolescents with MDD, reduced REM latency findings occur in inpatient samples (and in one outpatient study with uniform bedtimes). Two interpretations could account for these findings: 1) They could result from differences in inpatient samples (e.g. severity of illness, comorbidity, or suicidality). 2) These differences could result from some aspect of hospitalization. As will be presented in this proposal, evidence from adolescent sleep studies and from our own findings indicate sleep-wake schedules and/or adaptation effects are likely to be central to these findings. The purpose of this study is to substantiate this interpretation and to test two complimentary hypotheses: I) With precise control of sleep times and schedules in all subjects, reduced REM latency will be detected in both inpatient and outpatient MDD groups compared to normal adolescent controls. II) REM latency will e reduced further in MDD adolescents in response to transient sleep restriction (as often occurs during hospitalization). The following protocols will be utilized to test these hypotheses. Outpatient Protocol: Outpatient MDD adolescents and normal adolescent controls will follow a precise schedule for one week corresponding to the inpatient schedule monitored by activity meters, sleep log, and telephone verification. In the second week, three nights of sleep restriction, then two nights of recovery sleep. Inpatient Protocol: Inpatient adolescents with MDD will undergo five consecutive nights of EEg sleep recording (during the first week of admission) while adapting to the impatient unit. In the second week, they will follow the same schedule of baseline, partial sleep deprivation, and recovery sleep recording in the sleep lab as in the outpatient protocol. Data analyses will compare sleep measures between groups (inpatients, outpatients and controls) for each condition (baseline and recovery). Additional analyses will compare sleep variables across conditions of baseline and recovery sleep within each group. Within the inpatient group, analyses will also examine night to night changes during the transition period to the ward. This study addresses a central issue in the psychobiology of adolescent affective disorders. Delineating the roles of erratic sleep schedules, transient sleep restriction, and adaptation effects, is crucial to our understanding of sleep changes in adolescent MDD.